College Chemistry : Laws of Thermodynamics

Study concepts, example questions & explanations for College Chemistry

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Example Questions

Example Question #1 : Laws Of Thermodynamics

The second law of thermodynamics states which of the following is true regarding an isolated system?

Possible Answers:

The entropy can only increase

Energy in the form of heat is always conserved

The entropy approaches a constant value as the temperature of the system approaches zero Kelvin 

The entropy can only decrease

Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other

Correct answer:

The entropy can only increase

Explanation:

The entropy cannot decrease in an isolated system because the energy can only be degraded. Since the system is isolated, no higher-grade energy—or any energy at all—is being introduced into the system. As a result, the entropy cannot decrease. The other answer choices relate to the other laws of thermodynamics. 

Example Question #1 : Laws Of Thermodynamics

Which of the following statements is true of standard states?  

Possible Answers:

Solute of  concentration 

Solute in  of solution 

Gas at 

Gas at  pressure

Temperature at 

Correct answer:

Gas at  pressure

Explanation:

Standard states are defined as a specific set of conditions, such as when a gas is at  concentration, and .  

Standard enthalpy of formation, the energy required for form 1 mole of a compound from its constituent elements, occurs when elements are in their standard states. 

Example Question #3 : Laws Of Thermodynamics

How much heat is required to raise the temperature of  of water from  to ?  (Specific heat capacity of water is )

Possible Answers:

Correct answer:

Explanation:

 is positive because heat flows into the system to raise the temperature of the water.

Example Question #4 : Laws Of Thermodynamics

How much heat is required to raise the temperature of  of water from  to ? Specific heat capacity of water is 

Possible Answers:

Correct answer:

Explanation:

Example Question #5 : Laws Of Thermodynamics

"In a natural thermodynamic process, the sum of the entropies of the interacting systems increases." Which law of thermodynamics does this statement refer to?

Possible Answers:

First law of thermodynamics

Second law of thermodynamics

Zeroth law of thermodynamics 

Third law of thermodynamics

Correct answer:

Second law of thermodynamics

Explanation:

There are four main laws of thermodynamics, which describe how temperature, energy, and entropy behave under various circumstances. The zeroth law of thermodynamics helps to define temperature; it states that if two systems are each in thermal equilibrium with a third system, they must be in thermal equilibrium with each other. The first law of thermodynamics negates the possibility of perpetual motion; it states that when energy passes into or out of a system, the system's internal energy changes in accord with the law of conservation of energy. The second law of thermodynamics also negates the possibility of perpetual motion; it states that in a natural thermodynamic process, the sum of the entropies of the interacting systems increases. Lastly, the third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature nears absolute zero.

Example Question #6 : Laws Of Thermodynamics

Calculating heat

How much heat is absorbed by a copper penny as it warms from  to  assuming the penny is pure copper with a mass of ?  of copper is .

Possible Answers:

Correct answer:

Explanation:

Use the equation that relates heat, mass, specific heat, and change in temperature:

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